rtld: fix processing of preloaded z_initfirst objects

After we found some preloaded z_initfirst object, we must process till
the end of the preload list still, not stopping on the first found
object.

Reported by:	des
Reviewed by:	des, markj, siderop1@netapp.com
Fixes:	78aaab9f1c
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D56466

libexec/rtld-elf/rtld.c

@@ -2654,6 +2654,11 @@ initlist_add_objects(Obj_Entry *obj, Obj_Entry *tail, Objlist *list,
 			initlist_add_neededs(obj->needed_aux_filtees,
 			    NULL, iflist);
 		objlist_push_tail(iflist, obj);
+
+		/* Recursively process the successor objects. */
+		nobj = globallist_next(obj);
+		if (nobj != NULL && obj != tail)
+			initlist_add_objects(nobj, tail, list, iflist);
 	} else {
 		if (obj->init_scanned)
 			return;